ALBERT EINSTEIN had many passions beyond his physics. He spent much time thinking, writing and speaking on nuclear disarmament, human rights, democracy, education reform, even reducing the conflict between Arabs and Jews. Less well known, however, are his contributions to philosophy.
Einstein thought deeply about the nature of knowledge and of reality, about scientific theories and their relation to the world. He often wondered how the hidden, unseen world that his equations described was possible. How is it that the mind can venture into realms of knowledge divorced from our everyday experiences? Einstein answered with a bold philosophical conviction: our minds have access to the reality beyond that we can see.
This was a controversial, even audacious statement to make, though not at all out of character, for Einstein was rarely afraid of wading into the deep waters of new disciplines.
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His take on philosophy stood in contrast to the emerging views among European philosophers of his day, such as those discussed in the weekly meetings of what was known as the Vienna Circle of philosophers.
Members of the Vienna Circle, also known as positivists, believed there is no such thing as inherent knowledge, but that knowledge is gained through experience and experiment. These ideas were powerful, and contributed to a widespread view that it is not possible to chance upon a description of the workings of the universe through thought alone. The prevailing view today remains that science allows us to model the world, and in turn to make predictions, but not to delve into some Platonic realm of truth that exists independently of anything that can be analysed or measured.
Einstein, however, disagreed. He began a passionate exchange with Moritz Schlick, the Vienna Circle鈥檚 founder, and Hans Reichenbach. Though he was not a professional philosopher, the subject was comfortable ground for Einstein. His true teachers had never been physicists but other European philosophers such as Baruch Spinoza, Immanuel Kant and Pierre Duhem, whose work he studied fervently while cutting his physics classes, along with the philosophical works of Ernst Mach and Jules-Henri Poincar茅.
Einstein believed that although we start and end with experience, in the middle lies something else 鈥� something not accessible to the telescope or to the microscope, but only to the mind. At the heart of his philosophy was the distinction he made between two kinds of scientific theories: 鈥渃onstructive鈥� theories and 鈥減rincipled鈥� ones.
According to Einstein, constructive theories are models that describe phenomena based on known facts. While they are accurate representations of the world of experience, constructive theories lack unifying principles to explain why the world is as it is. Principled theories, in contrast, are deductive: you start with the principles that underlie the theory and then work down to deduce the facts.
For example, Einstein鈥檚 theories of relativity are principled theories. The principles are known: the speed of light is constant, the laws of physics are the same for everyone, and there is an equivalence between gravity and acceleration. From these basic principles, reality unfurls. On the other hand quantum theory, in Einstein鈥檚 view, is an example of a constructive theory. It describes phenomena based on some known facts, but an underlying principle to explain the strangeness of the quantum world has not yet been found.
Where should we look to discover the principles that underpin reality? In Einstein鈥檚 view, while facts reside in the world, principles reside in the mind. A physicist, he said, starts by looking at the facts and tries to 鈥渨orm the general principles out of nature鈥�. To find these requires a leap into the unknown, into the darkness of the mind where intuition and imagination hide. 鈥淭he theoretical idea does not arise apart from 鈥� and independent of 鈥� experience; nor can it be derived from experience by a purely logical procedure. It is produced by a creative act,鈥� Einstein wrote.
Einstein insisted that great theories are those that explain the most facts from the least number of principles. This was his aesthetic of simplicity, and it was rooted in his belief that the simpler the theory, the less it will look anything like the world we see. The ultimate goal of science, he believed, is to find one all-encompassing, self-evident principle or set of principles from which the whole of reality can be deduced. 鈥淭he supreme task of the physicist,鈥� he wrote, 鈥渋s to arrive at those universal elementary laws from which the cosmos can be built up by pure deduction. There is no logical path to these laws; only intuition, resting on sympathetic understanding of experience, can reach them.鈥�
Many today disregard Einstein鈥檚 philosophy because they feel that it downplays the importance of group collaboration and rigorous experimentation. Martin Rees, the new president of London鈥檚 Royal Society, for example, said recently that one downside to Einstein鈥檚 fame is that it perpetuates what he considers to be the 鈥渕yth鈥� of armchair physics. This view follows in the tradition of the Vienna Circle and rejects the notion that truth resides anywhere other than in the observable world, and it leaves little room for art or intuition in the scientific method. It clearly fits in well with what the philosopher Thomas Kuhn called 鈥渘ormal science鈥�, the daily grind of the great scientific machine as people go about the routine business of hypothesis, experiment and incremental advance in understanding. But science occasionally undergoes more profound revolutions in our understanding of the world, based upon new ideas that spring from the minds of those who propose them. For example, physicists today are searching for new ideas to explain the relationship between general relativity and quantum mechanics. As they search for an explanation, they don鈥檛 have many observations and experiments to work from. What they need are principles, and the assurance that the human mind is a portal to scientific truth.
鈥淓instein was rarely afraid of wading into new disciplines鈥�
Einstein鈥檚 confidence in the power of human thought was the key to his success. His physics depended on it. The famous photograph of Einstein peering through Edwin Hubble鈥檚 telescope on Mount Wilson to see the expansion of the cosmos pays tribute to his philosophy. The idea that what one man dreamed up in a shoddy room somewhere is actually playing itself out in the enormous reality of the universe underlines the power of the mind and the exquisite potential of science. 鈥淥ne may say 鈥榯he eternal mystery of the world is its comprehensibility鈥�,鈥� wrote Einstein. 鈥淭he postulation of a real external world would be senseless without this.鈥�
